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4.1.1 Basic concepts of organic chemistry

Definitions

Term Definition
Functional group A group of atoms responsible for the characteristic reactions of a compound
Homologous series A series of organic compounds having the same functional group but with each successive member differing by \(CH_2\)
Saturated All carbon to carbon bonds are single bonds
Unsaturated Contain carbon to carbon multiple bonds (\(C=C\) or \(C \equiv C\))
Hydrocarbons Substances containing carbon and hydrogen atoms only
Isomerism Compounds with the same molecular formula but different arrangements of atoms in space
Structural isomers Compounds with the same molecular formula but different structural formulae

Basic definitions

Alkyl group

  • General formula \(C_nH_{2n+1}\)
  • Found on side chains of organic molecules

Types of hydrocarbons

  • Aliphatic
    • A compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings
  • Alicyclic
    • An aliphatic compound arranged in non-aromatic rings with or without side chains
  • Aromatic
    • A compound containing a benzene ring

Stem prefix

Number of carbon atoms Prefix
1 Meth-
2 Eth-
3 Prop-
4 But-
5 Pen-
6 Hex-
7 Hept-
8 Oct-
9 Non-
10 Dec-

Types of formulae

  • General formula
    • The simplest algebraic formula of a member of a homologous series
    • e.g. for an alkane: \(C_nH_{2n+2}\)
  • Structural formula
    • The minimal detail that shows the arrangement of atoms in a molecule
    • e.g. for butane: \(CH_3CH_2CH_2CH_3\) or \(CH_3(CH_2)_2CH_3\)
  • Displayed formula
    • Shows the relative positioning of atoms and the bonds between them
    • e.g. for ethanol
      • Exported image
  • Skeletal formula
    • The simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups
    • e.g. for butan-2-ol
      • Exported image
    • Cyclohexane
      • Exported image
    • Benzene
      • Exported image

Types of covalent bond fission

  • Homolytic fission
    • Each bonding atom receiving one electron from the bonded pair forming 2 radicals
  • Heterolytic fission
    • One bonding atom receiving both electrons from the bonded pair
    • The atom that takes both electrons becomes a negative ion
    • The atom that does not take the electrons becomes a positive ion
    • e.g. \(H_3C-Cl \rightarrow H_3C^+ + Cl^-\)

Radical

  • A species with an unpaired electron
  • Represented with a dot (\(\bullet\))
  • e.g. \(H_3C-CH_3 \rightarrow H_3C\bullet + \bullet CH_3\)

Curly arrows

  • Showing the movement of an electron pair
  • Showing either heterolytic fission or formation of a covalent bond
  • Exported image

Types of reaction

  • Addition reaction
    • Two or more reactants join together to form one product
  • Substitution reaction
    • An atom or group of atoms is replaced by a different atom or group of atoms
  • Elimination reaction
    • Involves the removal of a small molecule from a larger one
    • One reactant molecule forms two products